P10424 [Lanqiao Cup 2024 NOI Qualifier B] Good Numbers

If an integer, when read from the lowest digit to the highest digit, has odd digits in odd positions (ones, hundreds, ten-thousands, ...) and even digits in even positions (tens, thousands, hundred-thousands, ...), then we call it a "good number". Given a positive integer $N$, compute how many good numbers there are from $1$ to $N$.

An integer $N$.

An integer representing the answer.

### Explanation for Sample 1 The good numbers within $24$ are $1,3,5,7,9,21,23$, for a total of $7$. ### Constraints - For $10\%$ of the testdata, $1 \leq N \le 100$. - For all testdata, $1 \le N \leq 10^7$. Translated by ChatGPT 5